If any man willeth to do (ean ti qelh poiein). Condition of third class with ean and present active subjunctive qelh not used as a mere auxiliary verb for the future "will do," but with full force of qelw, to will, to wish. See the same use of qelw in Acts 5:40 "and yet ye are not willing to come" (kai ou qelete elqein). He shall know (gnwsetai). Future middle indicative of ginwskw. Experimental knowledge from willingness to do God's will. See this same point by Jesus in Acts 5:46 ; Acts 18:37 . There must be moral harmony between man's purpose and God's will. "If there be no sympathy there can be no understanding" (Westcott). Atheists of all types have no point of contact for approach to the knowledge of Christ. This fact does not prove the non-existence of God, but simply their own isolation. They are out of tune with the Infinite. For those who love God it is also true that obedience to God's will brings richer knowledge of God. Agnostic and atheistic critics are disqualified by Jesus as witnesses to his claims. Of God (ek tou qeou). Out of God as source. From myself (ap emautou). Instead of from God.